Using piezoelectric transducers in string instruments is well known in the art. For example, U.S. Pat. No. 5,410,101 is referred to a piezoelectric assembly clamped between a string holder and a bridge, provided with a dual layer arrangement of piezoelectric elements kept in contact with corresponding positive electrodes. The piezoelectric elements closer to the string holder detect string vibrations and the piezoelectric elements closer to the bridge detects body vibrations of the string instrument so that electric signals from piezoelectric elements of different groups can be tactfully blended together for rich and voluminous generation of musical tones over a wide tone range.
U.S. Pat. No. 6,822,156 of Lazarus et al. is referred to an acoustic guitar having two components that provide the signal that is representative of the guitar sound, a primary pickup device and a secondary pickup device. The primary device is the piezoelectric pickup that is situated between the strings beneath the saddle of a stringed instrument. The primary device is designed to detect the bulk of the sound as well as the tonal nuances. The secondary device as used in one embodiment of this invention makes use of the physically induced charge modulation properties along both the longitudinal and transverse axis of the interconnecting coax cable that runs from the primary pickup to the impedance changing preamplifier. An optional pair of pickups may be disposed outside the strings. Also, a compressible gasket may be placed between the pickup and saddle and the pickup and the bridge to prevent air gaps thereinbetween.
U.S. Pat. No. 6,515,214 of Takabayashi describes a pickup unit used for converting vibrations of strings to electric signals for producing electric tones at good loudness, and the pickup unit including a bridge assembly stationary to a body of the stringed instrument, vibration-responsive piezoelectric elements secured at the end portions thereof to the bridge assembly and vibration mediators held in contact with the strings and exerting force on the other end portions of the piezoelectric elements; since the vibration mediators have the freedom to move in the direction of the bending in the bridge assembly, the electric signals exactly represent the vibrations of the strings.
U.S. Pat. No. 6,274,801 of Wardley claims an instrument pickup assembly comprising, a piezoelectric transducer configured for association with a belly of a stringed instrument, a transmittable conduit associated with said piezoelectric transducer at a first end thereof, and means for securely positioning said piezoelectric transducer onto said belly of said stringed instrument.
U.S. Pat. No. 6,075,198 is referred to a rigid, solid bodied stringed instrument having an electrical pickup embedded in at least one predetermined position within the stringed instruments solid body to pick up the actual wood tones and resonance of the rigid solid body. The electrical pickup is comprised of a piezoelectric transducer embedded between a planar brass surface and a planar ceramic surface. In the preferred embodiment, the pickup transducer is circular in shape and embedded within the stringed instrument's solid body adjacent the strings which span the body. The embedded piezoelectric transducer requires a fraction of the area required by traditional electric coil pickups. In an alternate preferred embodiment, the pickup transducer is embedded within transducer housing. The housing is then embedded within the solid body of a stringed instrument adjacent the strings. By including the piezoelectric transducer within its own housing the pickup can be sold separately in the aftermarket and incorporated in solid body stringed instruments.
U.S. Pat. No. 6,023,019 refers to a stringed instrument, such as a guitar including a saddle for holding the strings and a pickup assembly for converting vibrations of the strings into electrical signals, the saddle has a curved bottom surface for contacting the pickup assembly. The pickup assembly is formed in flexible layers, including a first layer of insulation, a second layer of piezoelectric film with a ground lead on top, a third layer having contacts formed thereon in positions corresponding to the strings to create active areas in the film underneath the strings, the third layer having lead lines disposed at the bottom thereof, and additional lead lines at the bottom of a fourth flexible layer. Electrodes communicate one end of the lead lines with the contacts via through-holes in the intervening layers. The other ends of the lead lines fasten to pins which connect to an amplifier circuit.
U.S. Pat. No. 5,817,966 of Fishman refers to a transducer for a stringed musical instrument incorporating an electrically conductive ground plane, along with a piezoelectric transducer and a conductive strip. The piezoelectric transducer is comprised of a polyvinylidene fluoride co-polymer. The ground plane, piezoelectric transducers and conductive strip are secured in an elongated unitary structure with the ground plane and conductive strip disposed on opposite sides of the transducers. A conductive shield is disposed about the unitary structure and electrical leads connect to the ground plane and conductive strip, respectively. The transducer may also include two piezoelectric transducers and conductive strips to provide two different outputs from the transducer. The two piezoelectric transducers may have different frequency response characteristics or may be connected to different signal processing circuits to allow for distinct modulations and mixing of outputs.
U.S. Pat. No. 5,463,185 of Fishman claims a transducer for a stringed musical instrument incorporating an electrically conductive ground plane, along with a piezoelectric transducer and a conductive strip. The piezoelectric transducer is comprised of a polyvinylidene fluoride co-polymer. The ground plane, piezoelectric transducers and conductive strip are secured in an elongated unitary structure with the ground plane and conductive strip disposed on opposite sides of the transducers. A conductive shield is disposed about the unitary structure and electrical leads connect to the ground plane and conductive strip, respectively.
U.S. Pat. No. 5,322,969 claims a piezoelectric transducer saddle with a thin, generally rectangular member that is designed to fit into the bridge slot of a musical instrument such as a guitar. The piezoelectric element is oriented vertically in the saddle and constitutes a structural member of the saddle. In a first embodiment of the saddle, a piezoelectric element forms the saddle itself. Electrical contacts are engaged to the sides of the piezoelectric element to produce electrical output. A preferred embodiment of the saddle is a laminated structure wherein the laminated layers are disposed vertically, and a vertical layer composed of a piezoelectric material is generally centrally disposed within the laminated structure. A metallic electrical contact is engaged on each side of the piezoelectric material to receive electrical signals generated by the piezoelectric material. In one embodiment, one of the electrical contacts is formed as a metallic layer which rises to the upper surface of the saddle to make contact with the strings of the musical instrument, in order to provide a ground for the metallic musical strings of the instrument. Further embodiments of the present invention utilize multiple piezoelectric elements and shaped piezoelectric elements to produce enhanced performance.
U.S. Pat. No. 5,078,041 refers to a suspension bridge pickup mechanism for stringed musical instruments. Vibrations from the strings are transferred to a suspended bridge which is in contact at spaced points with resonator plates of a plurality of bimorphic piezoelectric elements. The bridge has a high length to transverse thickness ratio resulting in a signal of wide frequency range and high amplitude. The tonal characteristics and the relative harmonic content of the signal can be altered by selecting or rejecting specific transducers which will contribute to the output signal utilizing a switching circuit. The transducers may be positioned under different portions of the bridge resulting in greater low frequency response In the median region of the bridge, maximal mid frequency response in the paramedian region, and maximal high frequency response near the ends of the bridge. Resonator plates of large area and small thickness are employed for maximal reproduction of low frequencies and resonator plates of small area and greater thickness are employed for maximal reproduction of high frequencies. The instrument strings cross and is supported by the bridge asymmetrically of its length.
There are many string instruments, such as guitars and violins that are equipped with electroacoustic devices for the controlled reproduction of sound so as to reach higher volumes. Among known systems is the incorporation of a microphone inside the sound box of the instrument, where the microphone picks up the sound already produced and sent out by the instrument and transforms it into a signal that is amplified by an amplifier for its controlled reproduction. This results in a significant increase in the reproduction volume of the sound because the volume is determined by the amplifying devices; however, the quality of the sound reproduced is not good and the sound differs from the true one produced by the acoustic instrument.
In order to improve reproduction trying to make it as similar to the original sound as possible, piezoelectric microphones are used, which are placed under the bridge of said instrument to pick up the vibrations of the strings and the sound generated inside the sound box directly. This has improved sound quality compared to a microphone placed inside said sound box, but the sound is still not genuine and this use is restricted to certain types of music, such as jazz, rock, etc., and it is not used in those cases where the “purity” of the sound is relevant itself, for example, in a classic guitar concert, a violin concert, etc. In other words, the sound that is reproduced and amplified is still not similar to that of an acoustic string instrument.
Even though the use of piezoelectric transducers has notably improved the quality of the amplified sound, the transducers used nowadays and their disposition do not take advantage of the differentiation, separation, and selection of the vibrations generated by the different strings to manage each of them, or at least part of them, separately. This is because instruments that use piezoelectric transducers in fact use a single transducer or transducer set placed on the bridge of the violin or in the saddle of the guitar. This single transducer receives all vibrations of the different strings and turns them into signals that are sent to a processing circuit for amplification and acoustic emission.
Whatever the tone of the vibrations might be, they are all picked up by the same transducer but it is well known that not all transducers are the same, so not all of them are equally adequate to pick up and reproduce different signals or vibrations. Some transducers are better at converting high-pitched sounds, while others are better at converting low-pitched sounds.
Consequently it is still a market need a new set or disposition of piezoelectric transducers for string instruments where the vibrations produced by the instrument are differentiated and better processed.